The mandrill is perhaps the most colorful primate. It has an olive green or dark grey pelage with yellow and black bands and a white belly. Its hairless face has an elongated muzzle with distinctive characteristics such as a red stripe down the middle and protruding blue ridges on the sides. It also has red nostrils and lips, a yellow beard and white tuffs. The coloration of the animal is more pronounced in dominant adult males.
Both genders have a patch of skin, surrounded by bristly hairs, on their chests that are used in olfactory communication. These too are more pronounced in dominant adult males. Males also have longer canines than females.
The mandrill has an omnivorous diet. It mostly consumes plant matter and consumes over hundred species of plant. It mostly eats fruit but will also eat leaves, lianas, bark, stems and fibers. It also consumes mushrooms and soil.With animals, mandrills mostly eat invertebrates, particularly ants, beetles, termites, crickets, spiders, snails and scorpians. It will also eat eggs, and occasionally vertebrates like birds, tortoises, frogs, porcupines, rats and shrews.
Mandrills seem to live in large stable groups called "hordes." Hordes often number in the hundreds, possibly averaging around 620 individuals and reaching as much as 845.